Selection of turbulence promoters for retrofit applications through thermohydraulic performance mapping

Abstract

Many new heat transfer enhancement devices have been reported in the open literature in the past decades exhibiting innovative geometries and better thermal and hydraulic performance. For a practical application in tubular heat exchangers, the selection of the best inserts out of the many different geometries available can be a cumbersome task. This work shows an approach to reduce the complexity of the search by graphically displaying the relative increase of heat load and pressure drop by means of performance mapping plots. The analysis includes the use of Nusselt and friction correlations and their application at different Reynolds numbers and different fluid viscosities. Out of the different geometries available, a group of 51 are compared in terms of the effect on heat duty and pressure drop. The approach is extended to analyse the exchanger irreversibility. For different operating conditions and fluid types, it is shown that the perforated twisted tape is the best performing insert. This insert produces an increase in heat transfer rate between 4% and 7.3% and an increment in pressure drop between 2 and 3.43 times that of the base case.